Personal audio devices, including wireless telephones, such as mobile/cellular telephones, cordless telephones, mp3 players, and other consumer audio devices, are in widespread use. Such personal audio devices may include circuitry for driving a pair of headphones or one or more speakers. Such circuitry often includes a speaker driver including a power amplifier for driving an audio output signal to headphones or speakers. Oftentimes, a power converter may be used to provide a supply voltage to a power amplifier in order to amplify a signal driven to speakers, headphones, or other transducers. A switching power converter is a type of electronic circuit that converts a source of power from one direct current (DC) voltage level to another DC voltage level. Examples of such switching DC-DC converters include but are not limited to a boost converter, a buck converter, a buck-boost converter, an inverting buck-boost converter, and other types of switching DC-DC converters. Thus, using a power converter, a DC voltage such as that provided by a battery may be converted to another DC voltage used to power the power amplifier. In addition, in some applications, a power converter may be implemented to provide electrical energy to a core analog and digital circuits of an audio processing integrated circuit. A power converter used in such a fashion may be referred to as a switch mode power supply.
A peak current controlled switch mode power supply operating in continuous conduction mode (CCM) may incur excessive power loss that significantly degrades efficiency under light load conditions. To achieve improved power efficiency across wide load current and input voltage ranges, traditional switch mode power supplies may transition between discontinuous conduction mode (DCM) and CCM and vice versa. However, excessive power loss in DCM operation becomes significant as switching frequency increases. Accordingly, this issue has been addressed by further employing pulse-skipping or pulse-frequency modulation (PFM) in lieu of DCM operation, which eliminates negative inductor current losses and reduction of switching losses through reduction of switching frequency. Existing techniques to provide PFM control in switch mode power supplies employ multiplexing between two control loops: a linear feedback and hysteretic PFM feedback control loop, in order to drive the power converter while regulating output voltage. However, such multiplexed approach complicates design and increases costs and time to market from a design and test perspective.